One form of workpiece clamping apparatus comprises a housing having inclined guides which, as viewed in radial planes thereof, extend inclinedly with respect to the axial direction. A plurality of clamping motion elements are displaceable along the guides and carry clamping jaws for clamping a workpiece to be clamped by the apparatus. A plurality of clamping pistons are associated with respective ones of the clamping motion elements, to provide for clamping the workpiece. The apparatus further includes a displacement actuation assembly which permits the clamping motion elements to be moved into respective released positions and clamping readiness positions in which the clamping motion elements are in a ready position to initiate clamping of the workpiece. An apparatus of that kind is to be found for example in DE-A 41 14 884.
That apparatus has a control member in the form of an actuation disk with the clamping pistons carried thereon, in order to draw respective projections of the clamping motion elements or like clamping bodies against the abutment surface of the actuation disk, thereby to permit displacement of the clamping motion elements. In that way the apparatus closes and the clamping jaws are caused to bear uniformly against the workpiece. The application of clamping pressure to the clamping pistons causes the workpiece which has been previously uniformly embraced to be clamped fast. While that apparatus operates satisfactorily and with a reasonable degree of precision, there are clamping reaction forces which make themselves noticeable at the actuation disk.
Another workpiece clamping apparatus as disclosed in EP 0 800 884 A2 involves the co-operation of motion-producing taper members which are guided in the axial direction and clamping jaws which are guided in radial directions, in order to bear gently against the workpiece before clamping pistons which are actuated by way of a presetting bar definitively clamp the workpiece fast.